The present invention is directed to an apparatus for detecting tumorous tissue, comprising at least one source of excitation light, which first excitation light source emits a first exciting light of a wavelength of between 300 nm and 314 nm and includes at least one optical fiber for guiding said first excitation light to an object field of the tissue to be examined, and at least one lens for projecting an auto-fluorescence signal and/or a remission signal of the tissue, generated by means of said first excitation light, to a CCD or ICCD chip of a camera, as well as at least one data processing system for processing the signals transmitted by the camera. The invention further relates to a method for detecting tumorous tissue.
Early detection of tumors is the most important prerequisite for fighting them effectively. This will also decisively improve tumor patients"" prospects of being cured. Prior art methods and apparatuses for detecting tumorous tissue are based on two different diagnostic approaches. One such approach is based on laser-induced fluorescence and involves administering synthetic fluorescent dyes or synthetic porphyrin mixtures as an attempt to label as well as display any tumours present. However, this method is disadvantageous in that the said synthetic substances will sensibilize the skin, thus requiring patients to be protected from intense light over a period of several weeks. Moreover, a low fluorescence quantum efficiency makes it impossible to distinguish clearly between healthy and abnormal tissue.
For this reason, it has been tried to gain information for distinguishing between healthy and tumorous tissue through the intrinsic, UV-excited auto-fluorescence of the tissue. The spectroscopic detection of tumours and neoplasia using UV light at between 300 nm and 312 nm is described in detail in U.S. Ser. No. 5,131,398 and WO 97/06724, for example. For this purpose, the tissue""s intrinsic fluorescence is excited by means of UV light at the said wavelength range, spectrally split by means of a spectrometer and then displayed. In doing so, the tissue is punctually scanned by means of a suitable optical probe. As a significant feature for distinguishing between normal healthy tissue and tumorous tissue, U.S. Ser. No. 5,131,398 discloses the intensity ratio of the native fluorescence in the fluorescence peaks at 340 nm and 440 nm.
However, one shortcoming of the prior art methods and apparatuses for displaying tumorous tissue by means of the auto-fluorescence of the tissue is that they do not provide a visual impression of the entire tumorous area or of the entire tissue area being examined.
For this reason, it is the object of the present invention to provide a generic apparatus as well as a generic method which will allow visual display of the entire tissue area under examination, at the same time clearly distinguishing normal healthy tissue from tumorous tissue.
This object is accomplished by a generic apparatus having the features of claim 1 as well as by a generic method having the features of claim 6.
Advantageous embodiments are described in the sub-claims.
An apparatus according to the invention for detecting tumorous tissue comprises a lens which is capable of processing UV light and is designed such that at least two images from different spectral regions of a fluorescent object field are generated and projected to a CCD or ICCD chip of a camera, with at least one of said images representing the UV range and another wavelength range, different therefrom, of the auto-fluorescence signal and/or of the remission signal of the object field. This will ensure that the entire tissue area being examined will be made visible, at the same time clearly distinguishing normal healthy tissue from tumorous tissue.
In an advantageous embodiment of the inventive device, the lens includes a ridge prism as well as at least one achromatic UV lens. Such an array will allow the illuminated object field to be precisely subdivided into plural images of different wavelength ranges of the auto-fluorescence signal and/or of the remission signal of the object field, which will then be displayed.
In yet another advantageous embodiment of the invention, the apparatus includes a second excitation light source for emitting a second excitation light at between 312 nm and 340 nm and/or 350 nm and 410 nm. Coupling in a second excitation light source emitting a second excitation light different from said first excitation light makes it possible to determine and process further image information about the object field. In certain cases, this will increase the selectivity of the apparatus for distinguishing between normal tissue and tumorous tissue.
An inventive method for detecting tumorous tissue comprises the following steps: (a) illuminating tissue with a first excitation light of a wavelength of between 300 nm and 314 nm from a first excitation light source and generating an auto-fluorescence and/or a remission of an object field of the illuminated tissue; (b) generating at least two images from different spectral regions of the fluorescent object field by means of a camera lens and projecting them to a CCD or an ICCD chip of said camera, with at least one of said images showing the UV range and another wavelength range, different therefrom, of the auto-fluorescence signal and/or of the remission signal of the object field; (c) transmitting the image/video signals generated in the camera to a data processing system; (d) subtracting background signals from the generated image/video signals; (e) inputting said UV image into a blue channel and computing said UV image therewith and inputting the other image into a green and/or red channel and computing it therewith; (f) amplifying or diminishing the individual color channels so as to obtain a standard color setting for normal, non-tumorous tissue; and (g) evaluating the color-coded images or their color-coded image/video signals for distinguishing normal, healthy tissue from tumorous tissue. This will in turn ensure that the entire tissue area being examined will be made visible, thereby clearly distinguishing normal healthy tissue from tumorous tissue.
In an advantageous embodiment of the method of the invention two images will be generated in procedural step (b), of which one image shows the UV range and the other image shows the visible wavelength range of the auto-fluorescence signal and/or the remission signal of the object field. Subsequently color coding the two images will result in a precise representation and quantification of the different kinds of tissue.
In yet another advantageous embodiment of the inventive method, procedural step (a) comprises illuminating the tissue with light from said first excitation light source and a second excitation light source for emitting second excitation light of a wavelength of between 312 nm and 340 nm and/or 350 and 410 nm. Using a second excitation light source emitting a second excitation light which is different from said first excitation light for illuminating said tissue makes it possible to determine and process further image information from the object field. In certain cases, this will increase the selectivity of the apparatus for distinguishing between normal tissue and tumorous tissue. In procedural step (b), for example, two images may be generated, of which one image shows the UV range and another image shows the infrared range of the auto-fluorescence signal and/or the remission signal of the object field. However, this will also make it possible to generate three images in procedural step (b), of which a first image shows the UV range, the second image shows the visible wavelength range, and the third image shows the infrared range of the auto-fluorescence signal and/or of the remission signal of the object field.
In accordance with another advantageous embodiment of the method of the invention, the color-coded images or color-coded image/video signals will be evaluated in procedural step (g) by comparing and displaying the generated standard color setting for normal, non-tumorous tissue with the generated color setting for tumorous tissue. This will allow the entire tissue area being examined to be made visible, at the same time clearly distinguishing normal tissue from tumorous tissue.
In yet another advantageous embodiment of the method of the invention, the evaluation of the color-coded images or color-coded image/video signals comprises the following sub-steps of procedural step (g): (g1) canceling the gamma correction by means of a correcting function and linearizing the color channels; (g2) obtaining the ratios of the intensities of the color channels and logarithmizing the result, in which step said tissue will be characterized in that positive values will denote tumorous tissue and negative values will denote normal, healthy tissue; and (g3) averaging the brightness values of the color channels and computing them together with a ratio image obtained in procedural sub-step (g2) for illustrating the distribution geometry of the different kinds of tissue. This illustration and evaluation approach allows a very precise quantification of the different kinds of tissue.